#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define rep(i, a, b) for (int i = (a); i <= (b); i++)
#define per(i, a, b) for (int i = (a); i >= (b); i--)
#define endl '\n'
const int N = 2e5 + 5;
const int MOD = 998244353;
mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());
int n, m;
int a[N];
void solve() {
  cin >> n;
  rep(i, 1, n) cin >> a[i];
  ll tot = 0, cnt = 0, cnt0 = 0;
  rep(i, 1, n) {
    if (a[i] == 1)
      cnt = (cnt + 1) % MOD, cnt0++;
    else if (a[i] == 2)
      cnt = cnt * 2 % MOD;
    else
      tot = (tot + cnt - cnt0 + MOD) % MOD;
  }
  cout << tot << endl;
}
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  int t;
  cin >> t;
  while (t--) solve();
  return 0;
}